1. Field of the Invention
The present invention relates generally to instruments and methods for inserting interbody spinal implants into an implantation space in the spine, and more particularly for use with expandable interbody (for placement at least in part between adjacent vertebral bodies in the space previously occupied by disc material) spinal fusion implants for the immobilization of vertebrae.
2. Description of the Related Art
Expandable spinal fusion implants have height raising capabilities that are utilized once the implant is initially positioned. Such height raising capability may be utilized within the spine anteriorly, posteriorly, or both and to various extents, respectively so as to raise the front, back, or both of the implant by the same or various amounts. More particularly, such implants have upper and lower surfaces of upper and lower members that in a first or insertion position are collapsed relative to one another and in a second or deployed position are adapted to contact the adjacent vertebral bodies.
Expandable fusion implants offer the advantage of allowing for the placement of a potentially larger implant through a smaller opening in a patient's body. Selective expansion along a single direction, (e.g. vertically only when correctly installed) offers the advantage of increasing the height of the implant and therefore the distraction of the disc space, but without a concomitant increase in the width of the implant.
Expandable fusion implants are known in the related art. The first expandable spinal fusion (allowing for the growth of bone from vertebral body to vertebral body through the implant) implant was invented by Michelson and also is disclosed in U.S. Pat. No. 5,776,199, filed Jun. 28, 1988, which is hereby incorporated by reference herein.
Push-in spinal fusion implants having upper and lower non-arcuate surfaces adapted for placement in contact with adjacent vertebral bodies are known in the related art. Such a push-in spinal fusion implant was invented by Michelson and is disclosed in U.S. Pat. No. 5,776,199, incorporated by reference above.
Push-in spinal fusion implants having upper and lower arcuate portions oriented toward the adjacent vertebral bodies and designed to engage the vertebral bodies along arcuate cuts therein typically formed by a drill are known in the related art. Such a push-in spinal fusion implant was invented by Michelson and is disclosed in U.S. Pat. No. 5,593,409, filed Feb. 17, 1995, which is hereby incorporated by reference. Push-in spinal fusion implants offer the advantage of being easily positioned in the implantation space and of having excellent fastening or holding features.
Threaded spinal fusion implants requiring rotation for insertion into the implantation space in the spine are known in the related art. The first artificial threaded spinal fusion implant was invented by Michelson and is disclosed in U.S. Pat. No. 5,015,247, which is hereby incorporated by reference. Threaded spinal fusion implants offer the advantage of being easily positioned in the implantation space and of having excellent fastening or holding features. Examples of instruments and methods of inserting spinal implants are taught by Michelson in U.S. Pat. No. 5,484,437 and U.S. Pat. No. 6,080,155, the disclosures of which are hereby incorporated by reference herein.
Lordotic or tapered, push-in spinal fusion implants are also known in the art. By way of example, Michelson has invented such implants as disclosed in U.S. Pat. No. 5,609,635, filed Jun. 7, 1995, which is hereby incorporated by reference. Lordotic, frusto-conical, or tapered, threaded spinal fusion implants are also known in the art. By way of example, Michelson has invented such implants as disclosed in U.S. Pat. No. 6,210,412, which is hereby incorporated by reference. Lordotic, frusto-conical, or tapered, push-in spinal fusion implants are also known in the art. By way of example, Michelson has invented such implants as disclosed in U.S. Application Ser. No. 08/484,928, filed Jun. 7, 1995, which is hereby incorporated by reference. Lordotic or tapered, spinal fusion implants have the advantage of restoring or enhancing spinal lordosis.
Expandable interbody spinal fusion implants preferably may be inserted from an anterior approach to the spine, an approach posterior to the vertebral transverse processes, to either side of the spinal midline in pairs, or from an anterior lateral approach to the spine. Such expandable implants are adapted to be capable of increasing in height anteriorly (at their leading ends) or posteriorly (at their trailing ends) from a first collapsed state, to a second expanded state for the purpose of increasing spinal lordosis at that interspace, or may be capable of increasing in height both anteriorly and posteriorly. During installation of expandable interbody spinal fusion implants, it is desirable that the surgeon have the ability to precisely control the implant with the appropriate instruments and methods to load the implant with appropriate bone growth promoting material, to insert the implant into the implantation space, to deploy the implant to a final expanded state, and to further load the implant with bone growth material if so desired.
There exists a need for instruments and methods for use with expandable interbody spinal fusion implants providing for all of the aforementioned needs individually or in combination.